Résumé
All of us are exposed to optical (i.e., visible and near-infrared) radiation from the sun and othersources throughout our lives. Assuming our eyes are shielded from excessive intensity, and ourskin is protected from the ultraviolet content of sunlight, we accept this exposure in theknowledge that it is perfectly safe. Unlike x-rays, optical photons are insufficiently energetic toproduce ionisation, and unless light is concentrated to such a high degree that it causes burningto the skin, optical radiation offers no significant hazard. The diagnostic potential of opticalmethods has been widely known since Jöbsis [1] first demonstrated that transmittancemeasurements of near-infrared (NIR) radiation could be used to monitor the degree ofoxygenation of certain metabolites. This led to the development and increasingly widespread useof clinical near-infrared spectroscopy (NIRS), which offers a safe, non-invasive means ofmonitoring cerebral function at the bedside without the use of radioisotopes or other contrastagents [2].